I knew because I've studied prehistory since my parents taught me to read at 4 years old by using a Little Golden Book titled "Then and Now". It is about reptiles, dinosaurs and early mammals. At that time, I decided I wanted to become a paleontologist. Unfortunately, when I was considering that and being a parapsychologist, I discovered that the colleges that offered these courses were too far away. *sigh* So, I majored in English/Liberal Arts and became a high school teacher.

I still keep up my studies of those two subjects. I was very surprised to see "Leptictidium" in your questions! I never imagined myself as a prehistoric creature and still can't.